1. Field of the Invention
The present invention relates to a piezoelectric transformer generating a desired output voltage by using a mechanical oscillation of a piezoelectric transducer.
2. Description of the Related Art
A piezoelectric transformer of this type is used, for instance, as high voltage power supplies of inverters for liquid crystal display back-lighting and the like, and generates a high voltage output from a low voltage input. To be in more detail, this transformer has a piezoelectric transducer housed in its case and the transducer has a function of transducing electric energy into mechanical energy. That is, owing to the mechanical oscillation of the transducer which is caused by the application of an input voltage to the transducer (a resonance phenomenon), a desired transformed output voltage is obtained.
Here, a primary electrode (Input) and a secondary electrode (Output) are formed on an outer surface of the transducer, the primary electrode being connected to an input-side terminal and the secondary electrode being connected to an output-side terminal. A technique using a tinsel wire for connecting the electrodes and the terminals is disclosed in Japanese Patent Application Laid-open No. Hei 6-342945, and techniques using conductive elastic members for connecting the electrodes and the terminals are disclosed in Japanese Patent Application Laid-open No. 2000-124519 and Japanese Patent Application Laid-open No. 2001-267647.
In the aforesaid case where the elastic member is used, there occurs no breakage of the tinsel wire or no peeling of soldered connection portions due to the oscillation of the piezoelectric transducer.
However, the use of the elastic members for connecting the electrodes and the terminals has a problem that the elastic members are easily displaced. This is because the elastic members are only press-fit between the electrodes and the terminals and are not firmly connected by soldering as is done in the aforesaid technique using the tinsel wire.
Moreover, the displacement of the elastic members can occur not only during the operation of the piezoelectric transformer but also during the assembly of the transformer.
This necessitates some measure for solving the displacement, but in the aforesaid conventional techniques, the elastic members are only press-fit between the electrodes and the terminals and this problem is still left unsolved.
Further, to solve this problem, the position where the piezoelectric transducer and the elastic members are in contact with each other needs to be considered. This is because, when the elastic members are to be press-fit, it is difficult to insert it from an opening into the deepest portion of the case. Moreover, the mechanical oscillation of the transducer occurs in a plurality of directions perpendicular to one another, and only with the consideration of the mechanical oscillation in one direction, the displacement of the elastic member still easily occurs.